Description:

An attempt was made to predict western spruce budworm defoliation using
egg counts from plots in the Douglas-fir type east of the Continental
Divide in Montana, the Douglas-fir type west of the Continental Divide
in Montana, and the mixed grand fir Douglas-fir type of northern Idaho.
The parameters used in a linear regression model for the three
ecotypes were eggs per 100 buds in 1972 as the independent variable and
percent defoliation in 1973 as the dependent variable. Correlation
coefficients (0 were: 0.39, 0.54, and 0.66 for the data from grand
fir in northern Idaho and Douglas-fir in eastern and western Montana
respectively. A covariance analysis of the three regression lines
showed there were differences between the three ecotypes.